[mirekrusin]

Yes, there are physical limits but they are so far off from human pov that they don't matter much.

For example information communication rate that humans can perform (read or write) compared to what computers can do.

Same with information storage, retrieval, precision, computation rate etc.

[ronald_raygun]

Sure computes have lots of transistors, but brains have 10s of billions of neurons and only use 12W of power.

[hackerlight]

If it's smarter than us it's pretty irrelevant whether it takes 12W or 5KW or even 1TW to run. Sure it may stop improving once it's far surpassed Von Neumann-level (at some point nobody knows) due to some physics or unknown information constraints but I don't think that has any practical bearing on much.